124 Cruise Control
 

Using this forum - and other troubleshooting resources - I am still unable to get my cruise control to work. Here's where I'm at:

1989 260e. All the bulbs replaced with new ones straight from the local Mercedes Dealer.

I pulled the underside dash cover. With my multi-meter, I tested the switch. All looks good.

I checked continuity between amp plug and actuator plug. All looks good.

I checked acuator motor. The solenoid sounds good. The motor I'm not sure about. It draws about 170mA from 12v, both directions. I heard a slight whirring (with a tint of grinding) noise from its general vicinity- but didn't see any movement. Should I see the arm move on the acutaor? If so - then I know the actuator is bad (or jammed or stuck).

I resoldered amp and reinstalled. Got the cuise to work on first test drive (at about 41mph)- but after shutting the car down, then starting up again - the cruise didn't work. It has worked twice since (both at under 50mph). Seems to be on cooler days after it has sat for a while (12+ hours).

I have a hunch (or false lead?)- that the temeprature has something to do with it. Seems that a warm engine (or warm ambient) may be creating some sort of thermal expansion that seizes something mechanically or shorts something electrically. But that's just a guess. Any thoughts? Others experience?

Also, I didn't mess with the Hall Sensor. Anyone have repair or troubleshooting experience with it? How often do they go bad?
Thanks.

The actuator should only be drawing about 130mA, not sure how much effect 170mA draw would have on the operation.